Carboxymethyl sesbania gum: Synthesis, characterization and evaluation for drug delivery

In the present study, carboxymethyl Sesbania gum was synthesized and evaluated for drug delivery. Carboxymethylation was carried out by reacting with monochloroacetic acid under alkaline conditions. Modification of the gum was confirmed by Fourier-transform infrared spectroscopy. The degree of carboxymethyl substitution was determined to be 1.3. Carboxymethylation improved the flow properties, increased the degree of crystallinity and changed the compression behaviour from elastic to plastic. Further, the interaction between the modified gum and Ca2+-ions was optimized employing a 3-factor, 3-level central composite experimental design to prepare mucoadhesive sustained release beads using metformin hydrochloride as the model drug. The optimal calculated parameters were- concentrations of carboxymethyl Sesbania gum-2.5%(w/v), metformin hydrochloride- 50%(w/w) and calcium chloride- 15%(w/v), which provided beads with%yield of 160 and entrapment efficiency of 39.3%. The optimized batch of beads released, 68% of metformin over 12 h, following the Higuchi's release kinetics with the mechanism of release being diffusion through the matrix.